Process of manufacturing photosensitive bodies



Patented Nov. 21, 1933 e e PROCESS OF MANUFACTURING PHOTOSEN- SITIVEBODIES Carl Roehrich, Berlin, Germany, assignor to the firm SilfreeAktienge'sellschaft (Silfree Limited) ,Vaduz, Lichtenstein No Drawing.Application January 9, 1929, Serial 'No. 331,384, and in Germany January21,

7 Claims. (Cl. 957) The present invention concerns an improved centageof salts in the solution, used for the immethod of manufacturingsensitive plates, films pregnation, the more sediment accrues. and thelike. The appearance of these sediments decreases It has been hithertoknown to manufacture considerably the usefulness of the plates ors'sensitive plates, films and the like, by'coating films. Firstly, thecolloid-layer being non-uni- 60 a support, consisting of glass,celluloid or any iorrnly sensitized, the light must act more Weaklyother transparent material or of thin metal foils, on the Weakersensitized parts of the layer than with a layer of colloids, such asgelatin, glues or on the stronger sensitized ones, causing irreguthelike, which is sensitized by impregnation with larities and shadows onthe subsequently pro- 10 suitable chemicals. duced picture. 5

Various means and numerous methods of im- A further source of faultslies in the alterations pregnating the plates and films are known.effected on the entering light by means of the Silver-salts are veryfrequently used as sensitizmore or less crystallized sediments, inasmuchas ing chemicals, the films, prepared with said salts, this light isreflected, broken and diffracted by on being exposed to the light,turning more or each single crystal face. It is therefore impossi- 70less dark at all parts which have been exposed ble for the enteringlight to penetrate such films to the light, uninterrupted, whereby thequality of the picture Other wellknown sensitizers cause the gelatinobtained is further impaired. to harden by the action of the light atthose Furthermore these sediments are nearly alparts of the film, whichhad been exposed to the Ways coloured, in most cases yellow, therebyact- 75 light, whilst the parts protected against the light g asColoured filters for the incident ht. are left soluble and absorbent.The present in- This impa the action of the ght, as coloured ventionrelates especially to plates, films and fi ter a knOWn tOebSOrb Parts Ofe light, the like, sensitized in this way, which therefore can not acton the deeper lay- After the exposure, the film hasto be subjected ersof the eolloid- The Sediments u cause so to a further treatment for thepurpose of rendere150 Considerable losses of light y- The ing thepicture visible. This can be reached, present invention has for its pu ps to avoid for example,.by the action of certain dyes or the d a esentioned above.

other sensitizers, which are absorbed by the non- Q Object of theinVentiOI} is to p p Sellhardened parts of gelatin, whilst the hardenedSltlVe plates, films and the llke, the surfaces of 85 parts are leftfree, which are free from sediments.

As sensitizers of this second type, chromic'acid Another f a of t nv nti to menusalts are generally used. The chromic acid salts factuleSensltlve e i SenS 1t1Zed h meansef are often applied to the plates orfilms together Chrome Salts, the sensltlzels helhg uniformly (1 S- withother metal salts in aqueous solution or in tllbuted throughout thecollold layer. 9o alcoholic solution diluted with water, the im- Afurther feafture 15 1 rrovldesuch SenSltlZed pregnation being frequentlyCarried out by im; layers, into which the ineident light may freelymersing the material to be sensitized in a bath m1nt'en:upted ydlffractmg f of the said solutions. ter absorption is 001m t stlu z ifipresen; m E pleted the films are subjected to a subsequent O p 2 t e dring process and are then ready for use. Sur ace 0 W t 15 tree 00 t q t yc thereby avoiding losses of energy of the incident On removmg the jsalqsensltlzlgg light, effected by absorption in the coloured sedibath,traces of the sensitizing solution remain menm 45 on the surface of thefilm, besides those parts From the foregoing can be seen that the of thesolution absorbed by the colloid layer. tures produced o such films rplates, free Thelough investigations have Shown that these fromsediments, will be clearer, sharper and free remaining traces are notuniformly distributed fro Shadows, veils and other irregularities, andover the sur ace of the film, but that they form that these good resultsmoreover can be attained 50 globules. Thus the surface looks like afatty by using for the exposure less light energy or urface, on whichwater has been applied. which is a very considerable advantage in prac-During the drying process, the liquid Solvent tical worka shorterduration of exposure than is evaporated from the globules and sedimentshith t V are formed on the surface of the film. It was first attemptedto achieve this end by 55 It was further found, that the higher thepertreating the films and the like with water, after impregnation withthe sensibilizing solution, where it was found that no or only the veryslightest decrease of sediment was effected by this treatment.Satisfactory results were, however, not reached by this method.

Further experiments showed that the treatment of the sensitive materialwith diluted alcohols gives very satisfactory results. For this purposethe sensitive films or plates, after inrpregnation with the sensitizingsolution as above mentioned, are subjected to the action of an alcohol.This treatment may be performed in any suitable way, for example byrunning the sensitive material under treatment through weak alcoholicsolution or by applying said solution to the sensitive surface of thematerial in any wellknown way.

When thus treated, the globules on the surface of the film disappear,the remaining traces of liquid are uniformly distributed over the wholesurface, and no sediments appear, when the film is dried.

This result may be considered as effected by loosening the surfacetension by the alcohol, thereby balancing the forces acting from thesurface of the film on the liquid.

A solution containing a 10% alcohol solution has been found sufficientfor most purposes. Ethyl alcohol for example may be used, other alcoholshowever giving good results too. Precaution must be taken with regard tothe duration of this treatment, as the aqueous solution naturallylixiviates the sensitized layer, and therefore may reduce thesensitiveness should the treatment be continued too long. It willsuflice in most cases to submit the film to the alcohol for about 12'seconds. As a rule the duration of this treatment is only a fraction ofthe previous time of impregnation, and may range for example between 10and 20, seconds.

The after-treatment described may be performed immediately after thesensibilization is concluded or before the sensitizing solution hasperfectly dried.

In the following a preferred form of this treatment is described as anexample, without however limiting the invention to theparticular detailsof the method, as given below.

A transparent film of celluloid is coated with a layer of gelatin, andis then, for the purpose,

of sensitizing, immersed in a bath containing:

Bichromate of ammonia gr.

Sulfate of copper l. 5 gr; Ammonia 200 ccm. Alcohol 150 com. Water 1000com.

After remaining in this bath for about 3 minutes, the film is removedand immediately transferred to a second bath containing 10% ethylalcohol in Water. After about 12 seconds, the film is removed andsubsequently dried. The drying is preferably carried out in one of thewellknown drying devices with warm air, a temperature of g about 23-24C. being suitable- For large scale manufacture the above proposedafter-treatment may be combined with the usual continuous process ofmanufacturing films. This may be done for instance by guiding the filmuninterruptedly and continuously through the second bath, after havingbeen sensitized-in the first bath, and by then drying the filmuninterruptedly and continuously.

From this method a film results, the surface of which is free fromsediments, and wherein the -sensitizers are uniformly distributed;During the exposure the light can enter freely into the colloid layerand can act freely on the uniformly distributed sensitive material. Forthe exposure less light-energy or a shorter duration of exposure isneeded, than with the films used hitherto, containing sediments.

Without further analysis, the foregoing will so fully reveal the gist ofthis invention that others can, by applying current knowledge, readilyadapt it for various utilizations by retaining one or more of thefeatures that, from the standpoint of the prior art, fairly constituteessential characteristics of either the generic or specific aspects ofthis invention and, therefore, such adaptations should be, and areintended to be, comprehended within the meaning and range of equivalencyof the following claims.

I claim:

1. The process of manufacturing photo-sensitive bodies having a colloidlayer, which comprises photo-sensitizing said layer with an agentadapted to harden the layer by reaction with light, and treating saidbodies with a dilute aqueous solution of an alcohol to free thephoto-sensitive surface of non-uniformly distributed sediments, thetreatment being continued for only a short time so as to leave thesensitivity of the,

said bodies substantially unimpaired.

2. The process of manufacturing photo-sensitive bodies having a colloidlayer which comprisesphoto-sensitizing said layer with an agent adaptedto harden the layer by reaction with light; and treating said bodieswith a dilute aqueous solution of an alcohol immediately after thesensitizing is completed to free the photosensitive surface ofnon-uniformly distributed sediments, the treatment being continued foronly a short time so as to leave the sensitivity of the said bodiessubstantially unimpaired.

3. The process of manufacturing photo-sensitive bodies having a colloidlayer whichcomprises photo-sensitizing said layer with an agentadaptedto harden'the layerby reaction with light; and treating saidbodies with a dilute aqueous solutionof an alcohol containing about 10%alcohol to free the photo-sensitive surface of non-uniformly distributedsediments, the treatment being continued for only a short time so as toleave the sensitivity of the said bodies substantially unimpaired.

4. The process of manufacturing photo-sensitive bodies having a colloidlayer which comprises photo sensitizing said layer with an agent adaptedto harden the layer by reaction with light; and treating said bodieswith a dilute aqueous alcoholic solution which containsabout 10% ofethyl alcohol to free the photo-sensitive surface of non-uniformlydistributed sediments, the treatment being continued for only a shorttime so as 'to leave the sensitivity of the said bodies substantiallyunimpaired.

5. The process of manufacturing photo-sensitive bodies having a colloidlayer which comprises photo-sensitizing said layer with an agent adaptedto harden the layer by reaction with light; and treating said bodies forabout 10 to-20 seconds with a dilute aqueous solution of an alcohol tofree the photo-sensitive surface of non-uniformly distributed sediments,and leav ing the sensitivity of said bodies substantially unimpaired.

6. The process of manufacturing photo-sensichromates and alcohol inaqueous solution; subsequently treating said bodies with a diluteaqueous solution of an alcohol to free the photo-sensitive surface ofnon-uniformly distributed sediments, the treatment being continued foronly a short time so as to leave the sensitivity of the said bodiessubstantially unimpaired.

CARL ROEHRICH.

